Portosystemic shunts (PSS) are vascular anomalies that divert bloodstream in the abdominal viscera towards the heart, skipping the hepatic sinusoids and transporting intestinal absorption items straight to the systemic circulation. Portosystemic shunts could be considered extrahepatic or intrahepatic, single or multiple, and hereditary or acquired. Kinds of single hereditary portovascular anomalies include intrahepatic portocaval shunts (i.e. patent ductus venosus) and extrahepatic portocaval or portal-azygos shunts. In a tiny number of dogs, the prehepatic portal vein can also be congenitally absent.
Single intrahepatic and extrahepatic PSS are often identified in immature creatures. No sex predilection is apparent. Single intrahepatic PSS are located mainly in large breed dogs for example Irish Wolfhound, Old British sheepdog, Golden and Labrador Retrievers, and Samoyed, as well as in medium-sized breeds for example Australian shepherds and Australian Cattle dogs. Single extrahepatic PSS occur mainly in small breed dogs like the Yorkshire terrier, Schnauzer, dog, Maltese, Shih Tzu, and dachshund. These shunts may connect the portal vein using the caudal vena cava directly, or may result from a portal tributary like the left gastric vein. Felines might have extrahepatic or intrahepatic shunts. Hereditary shunts are hereditary in Maltese and Irish Wolfhounds and can be hereditary in Yorkies.
Multiple extrahepatic PSS occur with chronic elevated hepatic portal venous resistance and portal pressure. These shunts are often found round the renal system. Breed predisposition for multiple PSS range from the German Shepherd and Doberman pinscher.
Stacey Zipfel